Change the Head or wiring

[jcorney]

A couple weeks ago I posted a video of an engine knock I had in a newly rebuilt motor in my 1977 XS400. It was determined that there was end play in the crank that was causing the knock. At some point I may rebuild this motor with new bearings, but for now I just want to ride the bike!!! So I picked up another motor. This motor has electronic ignition. The motor did not come with a wiring harness. I do have a harness from a 3rd motor I have, but I don't know if it is a points harness or a TCI harness. My question is, should I pull the head off my motor with the points and set the motor up to use points (which I know works properly) or try to get the TCI working? What do you think would be harder? I don't really want to pull the head, but I think the wiring could be a nightmare. The wiring harness on the bike has the pink coils for the points and the wiring harness I have in a box has the gray ones with the screw on wires. Not sure if that means it is for the TCI or not. If that harness is for a TCI motor that may be easier??? Does anyone know how I can tell? Then again, changing the harness out on the bike would suck too. Last question would be if I could put the points where the TCI unit is without changing out the head? The cover of course has the brass plug that I would have to figure out how to remove.

As you can see, I am at a loss as to what I should do. My gut says change the head, but...... I don't know!!

 

[xschris]

Just swap out to the points. Its easy. The heads are all the same on the motors.

 

[jcorney]

That's what I was thinking originally, but then I saw the brass plug in the right screw hole. Should I just drill that out? Also is the end of the cam shaft the same length?

 

[xschris]

Yep just drill out the plug to get to the screw. The cam end is the same for all sohc models and years.

 

[jcorney]

Well, I was able to drill out the plug and and get the cover off. Just ast you said, it looks like everything will fit just fine. That's the good news, the bad news is that I started to look over the rest of the motor I bought and found that the housing for the kickstarter is cracked... badly. Sooooo it looks like I am tearing a motor apart regardless. AWESOME!

 

[xschris]

Sorry to hear that

 

[drewpy]

there is a how to on the yam owners club changing from points to electronic.

To upgrade my xs400e I used parts from 80 or 81 xs400 machines:
o Pickup coil - 4R4-81671-10-00
o Rotor 3F9-81673-10-00 (will need longer bolt)
o Ignitor assembly 4R4-82305-10-00
o Ignition coils 2F3-82310-60-00 (you could use aftermarket high energy too)
o Ignition cover: 3F9-11157-00-00 (yep, your points cover is too shallow)

You can get part numbers from:
http://www.yamaha-mo...parts/home.aspx

If you want to make installation easier, get these too:
o Battery box - Ignitor mounts on the bottom. Easier than adapting old one.
o Wiring harness - untape an 80/81 xs400 wiring harness and lift out the wiring for the ignition
coil plugs, ignitor plug and the pickup coil plug. One snip each for power and gound
and you have all the wiring and plugs to add electronic ignition to your bike.
o xs400G Wiring diagram.

After you remove the points and condensor, there will be a red/white power connect left
hanging. Use that to power your new circuit. It comes right off the kill switch.
Add a connector to ground wire and find a place to bolt it onto the frame.

Make sure you have a good battery. You're adding more load and you want to keep your
voltage up when using electric start. Mikesxs has a maintenance free battery I have ordered
but not gotten yet that has 170cc amps.

Some ebay sellers say that the ignitor box from 82 works as well. But that is the year
the xs400 went to DOHC. Don't know if that makes a difference, but I just kept looking
if it came from an 82.

There was very little or no retooling to the cylinder head from 79 through 81 so parts will
fit nicely. Don't forget to set timing.

Most parts are no longer available from Yamaha. But everything can be found on ebay
with patience. I suggest getting spares if you go ahead with it.

Have fun!